PVC-free materials (non-PVC materials) and single-layer tubes produced therefrom with only one layer are known, by way of example, from WO 92/11820. This proposes a tube material for medical purposes which comprises a polyurethane polyester blend and which not only can be subjected to a sterilization treatment in an autoclave but also is hot-sealable and capable of high-frequency sealing and hot-frequency welding.
EP 0765740 discloses a PVC-free multilayer tube for medial purposes with at least two layers, of which a base layer A) composed of a first plastics material has been bonded to at least one connection layer B) composed of a second plastics material, where the first plastics material comprises at least one polymer which withstands heat sterilization at ≧121° C. without distortion, has a Shore D hardness ≦32, which at ≧121° C. has sufficient residual stress for pressure-fit at a connection point, and from which it is possible to form a coil or a loop with a diameter of down to 60 mm without undesired kinking, while the second plastics material comprises at least one polymer which during heat sterilization at 121° C. under the connection pressure resulting from pressure-fit has a tendency to flow and has a Shore A) hardness ≦65, thus ensuring that at temperatures ≧121° C. the plastics material has dimensional stability, while that of the second plastics material has been lost. Although the multilayer tube according to EP 0765740 can be used to obtain a flexible tube which is transparent after heat sterilization, which has adequate resistance to kinking, and which can be sealed using tube clamps or the like, and which moreover also has the capability to enter into firm and leakproof bonding to an insert, to a medical bag or to a connector, and indeed in an extremely simple manner during a possible heat sterilization treatment, the tube of EP 0765740 remains unsatisfactory in one respect.
Medical tubes are often shipped in coils. This is a space-saving method of transporting tubes without risk of tangling. Tubes can be held together in coils by threads, wires or clamps. However, in a particularly advantageous method, the outer layers of the tubes have been welded to one another in a peelable manner, so that the tubes form coils. In this embodiment, the coil can simply be pulled apart, with no prior need to release a means of holding, which then becomes waste. This also simplifies handling. The production of these coils welded in a peelable manner is described in U.S. Pat. Nos. 5,466,322 and 5,958,167.
When the coils of a tube according to EP 0765740 are separated, a possible consequence is that not only does the tube release from itself at the peelable weld but a crack is produced in the outer layer and can propagate into the inner layer. In the most disadvantageous case, damage to the tube in this process could be so great that a leak could occur. Particularly at low temperatures and if the coils are opened carelessly, the result can be damage which could render the tube unusable.